Device and method for controlling overload

ABSTRACT

An overload control device is disclosed. In one embodiment, the device includes a load measuring unit configured to measure the load of a radio network controller, wherein the network controller is in data communication with a plurality of base stations and an overload determining unit configured to determine whether an overload has occurred in the network controller based, at least in part, on the comparison of the measured load and a predetermined load. The device may further include a call connection controller configured to limit a new call connection setting of at least one base station which has a total transmission output greater than an allowed transmission output. The total transmission output indicates a power output of the base station for transmitting at least one call during a predetermined period. The allowed transmission output may vary according to the determined overload.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.12/179,484, filed Jul. 24, 2008, which is a continuation of PCTApplication No. PCT/KR2007/004461, filed on Sep. 17, 2007, each of whichis hereby incorporated by reference. PCT/KR2007/004461 claimed priorityto Korean Patent Application No. 10-2006-0106745 filed Oct. 31, 2006,which is hereby incorporated by reference in its entirety.

BACKGROUND

1. Field

The described technology generally relates to an overload control deviceand a method thereof in a mobile communication system, more specificallyto an overload control device and a method thereof in a radio networkcontroller.

2. Description of the Related Technology

A mobile communication service has been continuously developed since thefirst generation mobile communication service mainly having alow-quality voice call service provided by the advanced mobile phoneservice (AMPS) of an analog cellular type, which started in late 1980s.

In the second generation mobile communication service, it was possibleto provide an improved voice call service and a low-speed (14.4 Kbps)data service by the global system for mobile (GSM), the code divisionmultiple access (CDMA) and the time division multiple access (TDMA) of adigital cellular type.

In the 2.5th generation mobile communication service, it was alsopossible to provide an improved voice call service and a low-speed (144Kbps) data service by developing the personal communication service(PCS) that can be internationally used in addition to acquiringfrequency bands having the unit of GHz.

The third generation mobile communication service can be distinguishedinto two systems. One is the mobile communication system of anasynchronous type based on the generation partnership project (3GPP).The other one is the CDMA-2000 system of a synchronous type based on3GPP2. Especially, in the mobile communication system, which is thewireless protocol suggested in the IMT-2000, is being provided orprepared by a lot of worldwide communication service providers.

The mobile communication system, which has a high quality call serviceand uses a band diffusion method, is suitable to transmit a lot of data.

The WCDMA communication method employs the adaptable multi-rate (AMR)for voice coding and supports high mobility that can make it possible tocall to each other at a speed of 100 km/h.

The WCDMA communication method is also employed by most countries.Technical specifications for the WCDMA is continuously developed in the3GPP constituted by many institutes in Korea, Europe countries, Japan,USA and China.

Typically, service providers or network operators provides differentusers with various multi-media data services and/or voice communicationservices.

To provide the data services and/or the voice communication services,the service providers or the network operators manage wireless sourcesincluding system capacity and processing amount.

A mobile communication terminal can access a communication system and adifferent mutually accessed remote control communication system. Eacharea covered by radio networks are typically referred to as a cell. Eachradio network is set to receive an electromagnetic wave at a pilotoutput level in which it is enough to cover the cell. The pilot channelis downlink-broadcasted to make it possible to recognize cells and tomeasure received levels.

SUMMARY OF CERTAIN INVENTIVE ASPECTS

One aspect of the present invention is an overload control device and amethod thereof that can promptly and efficiently control an overload byconcentratedly controlling calls of base stations of an area in whichthe overload is generated when the overload is generated in a radionetwork controller.

Another aspect of the present invention is an overload control deviceand a method thereof that can prevent an output amplifier from beingdeteriorated and the quality of previously set calls from being loweredthrough efficiently controlling an overload by a radio networkcontroller.

Another aspect of the present invention features an overload controldevice in a mobile communication system.

According to an embodiment of the present invention, the overloadcontrol device can include a load measuring unit, measuring a load of aradio network controller every predetermined time; an overloaddetermining unit, determining whether an overload is generated bycomparing the measured load with a predetermined critical value; aparameter setting unit, setting a parameter of a call admission ratioaccording to an overload level if the overload is generated as theresult of determining, the call admission ratio indicating a ratio of amaximum transmitting output as compared with an admitted transmittingoutput of a base station; and a call connection setting control unit,transmitting to the radio network controller a call connection settingsignal to limit new call connection setting of a base station having atotal transmitting output value which is larger than an admittedtransmitting output value set by the parameter of the call admissionratio of the base station among all base stations pertained to the radionetwork controller.

Another aspect of the present invention features a method of controllingan overload in a mobile communication system.

According to an embodiment of the present invention, the method ofcontrolling an overload in a mobile communication system can includemeasuring a load of a radio network controller every predetermined time;determining whether an overload is generated by comparing the measuredload with a predetermined critical value; setting a parameter of a calladmission ratio according to an overload level if the overload isgenerated as the result of determining, the call admission ratioindicating a ratio of a maximum transmitting output as compared with anadmitted transmitting output of a base station; and transmitting to theradio network controller a call connection setting signal to limit newcall connection setting of a base station having a total transmittingoutput value which is larger than an admitted transmitting output valueset by the parameter of the call admission ratio of the base stationamong all base stations pertained to the radio network controller.

Another aspect of the invention is an overload control device in amobile communication system, the device comprising: i) a load measuringunit configured to substantially periodically measure a load of a radionetwork controller, ii) an overload determining unit configured todetermine whether an overload is generated based on the comparison ofthe measured load and a predetermined critical value, iii) a parametersetting unit configured to set a parameter of a call admission ratioaccording to a level of the determined overload, wherein the calladmission ratio indicates a ratio of a maximum transmitting output andan admitted transmitting output of a base station and iv) a callconnection setting control unit configured to transmit, to the radionetwork controller, a call connection setting signal to limit new callconnection setting of a base station having a total transmitting outputvalue which is larger than an admitted transmitting output value set bythe parameter of the call admission ratio of the base station among allbase stations associated with the radio network controller.

In the above device, information related to the measured load may berelated to i) calls set by being input into the base station associatedwith the radio network controller or ii) the total transmitting outputinformation of the radio network controller. In the above device, theparameter of the call admission ratio may be classified into at leastone overload grade according to the determined overload level. In theabove device, the parameter of the call admission ratio may comprise atleast three overload grades which are different from each other. In theabove device, the parameter of the call admission ratio may comprise aminor level, a major level and a critical level. In the above device,the call admission ratio of the minor level may be set to be higher thanthat of the major level, and wherein the call admission ratio of themajor level may be set to be higher than that of the critical level. Inthe above device, the overload control device may be configured to beincluded in the radio network controller as a part or as a separatedevice, to be linked with the radio network controller.

Another aspect of the invention is an overload control method in amobile communication system, the method comprising: i) substantiallyperiodically measuring a load of a radio network controller, ii)determining whether an overload is generated based on the comparison ofthe measured load and a predetermined critical value, iii) setting aparameter of a call admission ratio according to a level of thedetermined overload, wherein the call admission ratio indicates a ratioof a maximum transmitting output and an admitted transmitting output ofa base station and iv) transmitting, to the radio network controller, acall connection setting signal to limit new call connection setting of abase station having a total transmitting output value which is largerthan an admitted transmitting output value set by the parameter of thecall admission ratio of the base station among all base stationsassociated with the radio network controller.

In the above method, the measuring may comprise receiving informationrelated to calls set by being input into the base station associatedwith the radio network controller or the total transmitting outputinformation of the radio network controller. In the above method, thesetting may comprise classifying the overload level of the radio networkcontroller into a plurality of overload grades and setting the parameterof the call admission ratio differently according to the classifiedoverload grades. In the above method, the parameter of the calladmission ratio may comprise a lowest level, a middle level and ahighest level.

Another aspect of the invention is one or more processor-readablestorage devices having processor-readable code, the processor-readablecode which, when executed by one or more processors, performs anoverload control method in a mobile communication system, the methodcomprising: i) substantially periodically measuring a load of a radionetwork controller, ii) determining whether an overload is generatedbased on the comparison of the measured load and a predeterminedcritical value, iii) setting a parameter of a call admission ratioaccording to a level of the determined overload, wherein the calladmission ratio indicating a ratio of a maximum transmitting output andan admitted transmitting output of a base station and iv) transmitting,to the radio network controller, a call connection setting signal tolimit new call connection setting of a base station having a totaltransmitting output value which is larger than an admitted transmittingoutput value set by the parameter of the call admission ratio of thebase station among all base stations associated with the radio networkcontroller.

Still another aspect of the invention is an overload control device in amobile communication system, the device comprising: i) means forsubstantially periodically measuring a load of a radio networkcontroller, ii) means for determining whether an overload is generatedbased on the comparison of the measured load and a predeterminedcritical value, iii) means for setting a parameter of a call admissionratio according to a level of the determined overload, wherein the calladmission ratio indicates a ratio of a maximum transmitting output andan admitted transmitting output of a base station and iv) means fortransmitting, to the radio network controller, a call connection settingsignal to limit new call connection setting of a base station having atotal transmitting output value which is larger than an admittedtransmitting output value set by the parameter of the call admissionratio of the base station among all base stations associated with theradio network controller.

In the above device, the parameter of the call admission ratio maycomprise at least three overload grades which are different from eachother. In the above device, the parameter of the call admission ratiomay comprise a minor level, a major level and a critical level, whereinthe call admission ratio of the minor level may be set to be higher thanthat of the major level, and wherein the call admission ratio of themajor level may be set to be higher than that of the critical level.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram for illustrating a method of controlling an overloadin a typical radio network controller.

FIG. 2 and FIG. 3 are diagrams for illustrating a method of controllingan overload in a radio network controller in accordance with anembodiment of the present invention.

FIG. 4 is a block diagram illustrating an overload control device inaccordance with an embodiment of the present invention.

FIG. 5 is a flow chart illustrating a method of controlling an overloadin accordance with an embodiment of the present invention.

DETAILED DESCRIPTION OF CERTAIN INVENTIVE EMBODIMENTS

FIG. 1 is a diagram for illustrating a method of controlling an overloadin a typical radio network controller.

Referring to FIG. 1, the radio network controller (RNC) 110 can becoupled to various base stations through a T1/E1 line or circuit, an ATMvirtual circuit, a cable or an optical digital subscriber line (DSL).Typically, the radio network controller 110 controls the accessed basestations 120 through 170 and performs handover and provides an operationtime and a system management service.

If an overload is generated, the RNC 110 limits a transmitted call, areceived call and a position input number, input into the RNC 110, inorder to control the overload. In this case, since the calls input pereach base station are considered for the transmitted call, the receivedcall and the position input number, limited by the RNC 110, thedifference between the calls input in units of base stations 120 through170, accessed to the pertinent RNC 110, is not reflected. However, incase that the overload is generated after many calls are input into theRNC 110, the overload is mostly generated not because many calls areinput into the RNC 110 in all base stations 120 through 170 but becausemany calls are input into the RNC 110 in some base stations 120, 130 and140, for example, of a particular area.

Accordingly, the RNC 110 can more efficiently control the overloadthrough controlling calls of some base stations 120, 130 and 140, forexample, at a certain area into which many calls is input instead ofcontrolling all input calls.

Since there can be a variety of permutations and embodiments of thepresent invention, certain embodiments will be illustrated and describedwith reference to the accompanying drawings. This, however, is by nomeans to restrict the present invention to certain embodiments, andshall be construed as including all permutations, equivalents andsubstitutes covered by the spirit and scope of the present invention.Throughout the drawings, similar elements are given similar referencenumerals. Throughout the description of the present invention, whendescribing a certain technology is determined to evade the point of thepresent invention, the pertinent detailed description will be omitted.

Terms such as “first” and “second” can be used in describing variouselements, but the above elements shall not be restricted to the aboveterms. The above terms are used only to distinguish one element from theother. For instance, the first element can be named the second element,and vice versa, without departing the scope of claims of the presentinvention. The term “and/or” shall include the combination of aplurality of listed items or any of the plurality of listed items.

When one element is described as being “connected” or “accessed” toanother element, it shall be construed as being connected or accessed tothe other element directly but also as possibly having another elementin between. On the other hand, if one element is described as being“directly connected” or “directly accessed” to another element, it shallbe construed that there is no other element in between.

The terms used in the description are intended to describe certainembodiments only, and shall by no means restrict the present invention.Unless clearly used otherwise, expressions in the singular numberinclude a plural meaning. In the present description, an expression suchas “comprising” or “consisting of” is intended to designate acharacteristic, a number, a step, an operation, an element, a part orcombinations thereof, and shall not be construed to preclude anypresence or possibility of one or more other characteristics, numbers,steps, operations, elements, parts or combinations thereof.

Unless otherwise defined, all terms, including technical terms andscientific terms, used herein have the same meaning as how they aregenerally understood by those of ordinary skill in the art to which theinvention pertains. Any term that is defined in a general dictionaryshall be construed to have the same meaning in the context of therelevant art, and, unless otherwise defined explicitly, shall not beinterpreted to have an idealistic or excessively formalistic meaning.

Hereinafter, certain embodiments will be described in detail withreference to the accompanying drawings. Identical or correspondingelements will be given the same reference numerals, regardless of thefigure number, and any redundant description of the identical orcorresponding elements will not be repeated.

The present invention can be applied to various mobile communicationsystems. The below description is mainly related to a WCDMA mobilecommunication system for example.

FIG. 2 is a diagram for illustrating a method of controlling an overloadin accordance with an embodiment of the present invention.

In one embodiment, the overload control device 400 is connected to anRNC 210. When an overload is generated, a call admission controlfunction is operated, to thereby solve the overload efficiently bycontrolling calls of the base stations 220, 230 and 240, for example,into which the traffic is concentratedly input.

Referring to FIG. 2, the RNC 210 is connected to the overload controldevice 400 that controls the overload of the RNC 210.

The RNC 210 can be coupled to various base stations through a T1/E1 lineor circuit, an ATM virtual circuit, a cable or an optical digitalsubscriber line (DSL).

The radio network controller 210 controls the accessed base stations 220through 270 and performs handover and provides an operation time and asystem management service.

The base stations 220 through 270 perform voice communication and datacommunication with a mobile communication terminal (not shown) by thecontrol of the RNC 210.

The base stations 220 through 270 transmit total transmitting outputinformation to the overload control device 400. Here, the totaltransmitting output information, which refers to total outputinformation required to transmit a call during a predetermined period,can be energy of carrier/interference of other's (Ec/Io), for example,measured in the base stations 220 through 270.

The base stations 220 through 270 allows call connection setting to belimited by a call admission ratio set corresponding to an overload levelof the RNC 210.

For example, if an overload is generated in the RNC 210 because thetotal transmitting output of some base stations 220, 230 and 240, forexample, is higher than other base stations, the RNC 210 does not permitthe call connection setting for new calls of some base stations 220, 230and 240, for example, by the call admission ratio set corresponding tothe overload level.

Accordingly, the RNC 210 can control the overload of the RNC 210 bycontrolling some base stations 220, 230 and 240, for example, havingmuch traffic.

The overload control device 400 measures the overload level of the RNC210 and performs the call admission control corresponding to theoverload level of the RNC 210.

The overload control device 400 controls the RNC 210 to control the callinput for some base stations 220, 230 and 240, for example, into whichthe traffic is concentratedly input through call admission control.

Here, the overload level of the RNC 210 can be measured by measuring thenumber of calls set and input from all base stations 220 through 270 orthe total transmitting output of the RNC 210.

The overload control device 400 can determine a base station into whichthe traffic is concentratedly input by receiving a total transmittingoutput value of each base station 220 through 270 from all base stations220 through 270 during each predetermined period.

If the overload is generated in the RNC 210, the overload control device400 sets the call admission ratio corresponding to the overload level.

The overload control device 400 controls the RNC 210 to make itimpossible to set a new call for the base station having relative muchtraffic by setting the call admission ratio.

Accordingly, the overload control device 400 can control the overload ofthe RNC 210 by controlling call connection setting for a base stationinto which the traffic is concentratedly input.

The overload control device 400 will be described in more detail withreference to FIG. 4.

FIG. 3 is a diagram for illustrating a method of controlling an overloadin accordance with an embodiment of the present invention.

The call admission ratio, which is the ratio of maximum transmittingoutput as compared with the admitted transmitting output of the basestations 220 through 270, can be computed by the following formula 1.

Call admission ratio=Admitted transmitting output(Call AdmissionPower)/maximum transmitting output(Max Tx Power)  Formula 1

Here, the maximum transmitting output, which is dependable on equipmenttypes of each base station and output environments, is predetermined bya designer or an operator.

As described above, the overload control device 400 controls the RNC 210not to permit the call connection setting for new calls of some basestations 220, 230 and 240, for example, having much traffic by the calladmission ratio set corresponding to the overload level of the RNC 210.

Accordingly, the RNC 210 can control the overload.

Hereinafter, an overload control method will be described in more detailwith reference to (a) and (b) of FIG. 3.

In case that the admitted transmitting output, which is set by the calladmission ratio set corresponding to the overload level of the RNC 210,is larger than the total transmitting output of the base station, theoverload control device 400 controls the RNC 210 so as to allow new callconnection setting of some base stations 250, 260 and 270, for example,to be permitted.

However, in case that the admitted transmitting output, which is set bythe call admission ratio set corresponding to the overload level of theRNC 210, is the same as or smaller than the total transmitting output ofthe base station, the overload control device 400 controls the RNC 210so as to make it impossible to set new call connection of the pertinentbase station.

For example, if the call admission ratio set corresponding to theoverload level of the RNC 210 is 90%, the value corresponding to 90% ofthe maximum transmitting output of the base station is set as anadmitted transmitting output value.

Accordingly, in the base station having the larger admitted transmittingoutput corresponding to 90% of the maximum transmitting output valuethan the total transmitting output among the base stations pertained tothe RNC, a new call is permitted. However, in the base station havingthe same or smaller admitted transmitting output corresponding to 90% ofthe maximum transmitting output value as or than the total transmittingoutput among the base stations pertained to the RNC, a new call is notpermitted.

FIG. 4 is a block diagram illustrating an overload control device inaccordance with an embodiment of the present invention.

Referring to FIG. 4, the overload control device 400 includes a loadmeasuring unit 410 measuring the load of the RNC 210 every predeterminedtime, an overload determining unit 420 determining whether an overloadis generated by comparing the measured load with a predeterminedcritical value, a parameter setting unit 430 controlling a parameter ofcall admission ratio corresponding to an overload level and a callconnection setting control unit 440 transmitting a control signalcontrolling whether to permit new call connection setting of a basestation having much traffic among the base stations 220 through 270 by aparameter of the call admission ratio set corresponding to the overloadlevel. Here, the overload control device 400 can be included in the RNC210 as a part. Alternatively, the overload control device 400 can beconnected to the RNC 210 as an additional device.

The load measuring unit 410 measures the load of the RNC 210 everypredetermined time. Here, information related to the measured load ofthe RNC 210 can be the number of calls set by being input into the basestation 220 through 270 connected to the RNC 210 or the totaltransmitting output of the RNC 210.

The overload determining unit 420 determines the overload level of theRNC 210 by comparing the measured load of the RNC 210 received from theload measuring unit 410 with a predetermined critical value.

The overload determining unit 420 can classify the overload level of theRNC 210 into a minor level, a major level and a critical level. Theparameter of the call admission ratio controlling the overload accordingto the distinguished levels can be set to efficiently manage theresources of system according to the overload level.

The parameter setting unit 430 sets the parameter of the call admissionratio corresponding to the overload level. The parameters of the calladmission ratio set corresponding to the overload of the RNC 210 arecharted in the following table 1.

TABLE 1 Parameter Meaning Remark Critical_CA_Ratio Call admission ratio(%) when the load ratio is critical level Major_CA_Ratio Call admissionratio (%) when the load ratio is major level Minor_CA_Ratio Calladmission ratio (%) when the load ratio is minor level Normal_CA_RatioCall admission ratio (%) when an overload is not generated

The parameter of the call admission ratio can be classified into a minorlevel, a major level and a critical level corresponding to the overloadlevel. The classification standard is dependable on equipment types ofthe RNC 210 and surrounding environments, is predetermined by a designeror an operator.

Here, the minor level indicates the low overload level of the RNC 210,and the major level indicates the high overload level of the RNC 210.The critical level indicates the very high overload level of the RNC210.

Accordingly, the call admission ratio of the minor level can be set tobe higher than that of the major level. Also, the call admission ratioof the major level can be set to be higher than that of the criticallevel.

This is to efficiently manage the resources of system according to theoverload level.

The call connection setting control unit 440 transmits to the RNC 210 acontrol signal controlling whether to permit new call connection settingof a base station having much traffic among the base stations 220through 270 by a parameter of the call admission ratio set, as shown inthe above table 1, corresponding to the overload level of the RNC 210.

The call connection setting control unit 440, which is linked to anoperation server of a mobile communication system, stores maximumtransmitting electric power information of each base station.

Also, the call connection setting control unit 440 receives the totaltransmitting output information of all base stations 220 through 270pertained to the RNC 210 in order to determine the base stations havingmuch traffic among the base stations 220 through 270.

Here, the total transmitting output information, which refers to totaloutput information required to transmit a call during a predeterminedperiod, can be energy of carrier/interference of other's (Ec/Io)measured in the base stations 220 through 270.

The call connection setting control unit 440 controls the RNC 210 bygenerating a control signal restricting new call connection setting forthe base station in which the total transmitting output (total Tx power)per base station is larger than admitted transmitting outputcorresponding to the previously set call admission ratio. Here, sincethe call connection setting control unit 440 can compute admittedtransmitting output per base station corresponding to the previously setcall admission ratio by using the stored maximum transmitting outputinformation per base station, it is possible to compare the admittedtransmitting output per base station with the total transmitting outputper base station.

FIG. 5 is a flow chart illustrating a method of controlling an overloadin accordance with an embodiment of the present invention.

In a step represented by S510, the overload control device 400 measuresthe load of the RNC 210 every predetermined time. Here, informationrelated to the measured load of the RNC 210 can be the number of callsset by being input into the base station 220 through 270 connected tothe RNC 210 or the total transmitting output of the RNC 210.

In a step represented by S520, the overload control device 400determines whether an overload is generated in the RNC 210 by comparingthe load measured in the RNC 210 with a predetermined critical value. Ifit is determined that the overload is generated in the RNC 210, theoverload control device 400 performs an operation corresponding to anoverload control algorithm corresponding to each overload level.

In a step represented by S530, if it is determined that the overload isgenerated in the RNC 210, the overload control device 400 can classifythe overload level of the RNC 210 into a minor level, a major level anda critical level. Here, the minor level indicates the low overload levelof the RNC 210, and the critical level indicates the very high overloadlevel of the RNC 210. Accordingly, the call admission ratio of the minorlevel can be set to be higher than that of the major level. Also, thecall admission ratio of the major level can be set to be higher thanthat of the critical level.

The overload control device 400 can set the parameter of the calladmission ratio controlling the overload differently according to theclassified overload level. This is to efficiently manage the resourcesof system according to the overload level

In a step represented by S540, if the overload level is the minor level,the parameter of the call admission ratio of all base stations 220through 270 pertained to the RNC 210 is set as a predeterminedMinor_CA_Ratio.

In a step represented by S550, if the overload level is the major level,the parameter of the call admission ratio of all base stations 220through 270 pertained to the RNC 210 is set as a predeterminedMajor_CA_Ratio.

In a step represented by S560, if the overload level is the criticallevel, the parameter of the call admission ratio of all base stations220 through 270 pertained to the RNC 210 is set as a predeterminedCritical_CA_Ratio.

In a step represented by S570, the overload control device 400 generatesa control signal restricting new call setting in the base station inwhich the total transmitting output is higher than the admittedtransmitting electrical power corresponding to the parameter of the calladmission ratio in accordance with the overload level to the RNC 210.

Accordingly, the overload of the RNC 210 can be promptly and efficientlycontrolled by concentratedly controlling calls of the base stationshaving relatively much traffic.

The method according to embodiments of the present invention asdescribed above can be stored in a recorded medium (e.g. CDRom, RAM,ROM, floppy disk, hard disk, magneto-optical disk) having shapes capableof being realized with a program and readable by a computer.

At least one embodiment of the present invention can provide an overloadcontrol device and a method thereof that can promptly and efficientlycontrol an overload by concentratedly controlling calls of base stationsof an area in which the overload is generated when the overload isgenerated in a radio network controller.

At least one embodiment of the present invention can also provide anoverload control device and a method thereof that can prevent an outputamplifier from being deteriorated and the quality of previously setcalls from being lowered through efficiently controlling an overload bya radio network controller.

Hitherto, although some embodiments of the present invention have beenshown and described for the above-described objects, it will beappreciated by any person of ordinary skill in the art that a largenumber of modifications, permutations and additions are possible withinthe principles and spirit of the invention, the scope of which shall bedefined by the appended claims and their equivalents.

1. An overload control device in a mobile communication system, thedevice comprising: a load measuring unit configured to measure the loadof a radio network controller, wherein the radio network controller isin data communication with a plurality of base stations; an overloaddetermining unit configured to determine whether an overload hasoccurred in the radio network controller based, at least in part, on thecomparison of the measured load and a predetermined load; and a callconnection controller configured to limit a new call connection settingof at least one of the base stations which has a total transmissionoutput greater than an allowed transmission output, wherein the totaltransmission output indicates a power output of the at least one basestation for transmitting at least one call during a predeterminedperiod, and wherein the allowed transmission output varies according tothe determined overload.
 2. The overload control device of claim 1,wherein the load measuring unit is configured to measure the load basedon at least one of: i) the number of calls processed by the basestations and ii) the total transmission output of the radio networkcontroller.
 3. The overload control device of claim 1, furthercomprising: a call admission ratio calculator configured to calculate acall admission ratio according to the determined overload, wherein thecall admission ratio indicates a ratio of the maximum transmissionoutput and the allowed transmission output of the base station, andwherein the allowed transmission output is determined based, at least inpart, on the call admission ratio.
 4. The overload control device ofclaim 3, wherein the maximum transmission output is determined based atleast in part on equipment types and/or output environments of the basestation.
 5. The overload control device of claim 3, wherein the calladmission ratio is classified into at least one overload grade accordingto the determined overload level.
 6. The overload control device ofclaim 5, wherein the call admission ratio comprises at least threeoverload grades which are different from each other.
 7. The overloadcontrol device of claim 6, wherein the call admission ratio comprises aminor level, a major level and a critical level.
 8. The overload controldevice of claim 7, wherein the minor level is set to be higher than thatof the major level, and wherein the major level is set to be higher thanthat of the critical level.
 9. The overload control device of claim 1,wherein the load measuring unit is configured to substantiallyperiodically measure the load.
 10. The overload control device of claim1, wherein the total transmission output is a ratio of energy of carrierand interference of other's (Ec/Io) of the base station.
 11. An overloadcontrol method in a mobile communication system, the method comprising:measuring the load of a radio network controller, wherein the radionetwork controller is in data communication with a plurality of basestations; determining whether an overload has occurred in the radionetwork controller based, at least in part, on the comparison of themeasured load and a predetermined load; and limiting a new callconnection setting of at least one of the base stations which has atotal transmission output greater than an allowed transmission output,wherein the total transmission output indicates a power output of thebase station for transmitting at least one call during a predeterminedperiod, and wherein the allowed transmission output varies according tothe determined overload.
 12. The method of claim 11, further comprising:calculating a call admission ratio according to the determined overload,wherein the call admission ratio indicates a ratio of the maximumtransmission output and the allowed transmission output of the basestation, and wherein the allowed transmission output is determinedbased, at least in part, on the call admission ratio.
 13. The method ofclaim 11, wherein the measuring is performed based on at least oneof: 1) the number of calls processed by the base stations and 2) thetotal transmitting output information of the radio network controller.14. The method of claim 11, further comprising classifying the overloadlevel of the radio network controller into a plurality of overloadgrades, wherein the call admission ratio is calculated differentlyaccording to the classified overload grades.
 15. The method of claim 14,wherein the call admission ratio comprises a lowest level, a middlelevel and a highest level.
 16. The method of claim 11, wherein themeasuring comprises substantially periodically measuring the load.
 17. Aprocessor-readable storage device having processor-readable code, theprocessor-readable code which, when executed by one or more processors,performs an overload control method in a mobile communication system,the method comprising: measuring the load of a radio network controller,wherein the radio network controller is in data communication with aplurality of base stations; determining whether an overload has occurredin the radio network controller based, at least in part on, thecomparison of the measured load and a predetermined load; and limiting anew call connection setting of at least one of the base stations whichhas a total transmission output greater than an allowed transmissionoutput, wherein the total transmission output indicates a power outputof the base station for transmitting at least one call during apredetermined period, and wherein the allowed transmission output variesaccording to the determined overload.
 18. The device of claim 17,wherein the method further comprises: calculating a call admission ratioaccording to the determined overload, wherein the call admission ratioindicates a ratio of the maximum transmission output and the allowedtransmission output of the base station, and wherein the allowedtransmission output is determined based, at least in part, on the calladmission ratio.
 19. An overload control device in a mobilecommunication system, the device comprising: means for measuring theload of a radio network controller, wherein the radio network controlleris in data communication with a plurality of base stations; means fordetermining whether an overload has occurred in the radio networkcontroller based, at least in part, on the comparison of the measuredload and a predetermined load; and means for limiting a new callconnection setting of at least one of the base stations which has atotal transmission output greater than an allowed transmission output,wherein the total transmission output indicates a power output of thebase station for transmitting at least one call during a predeterminedperiod, and wherein the allowed transmission output varies according tothe determined overload.
 20. The overload control device of claim 19,further comprising: means for calculating a call admission ratioaccording to the determined overload, wherein the call admission ratioindicates a ratio of the maximum transmission output and the allowedtransmission output of the base station, and wherein the allowedtransmission output is determined based, at least in part, on the calladmission ratio.